Thermodynamics and Kinetic Modeling of the ZnSO4·H2O Thermal Decomposition in the Presence of a Pd/Al2O3 Catalyst

Abstract

The sulfur–iodine thermochemical water-splitting cycle is a promising route proposed for hydrogen production. The decomposition temperature remains a challenge in the process. Catalysts, such as Pd supported on Al2O3, are being considered to decrease reaction temperatures. However, little is known regarding the kinetic behavior of such systems. In this work, zinc sulfate thermal decomposition was studied through non-isothermal thermogravimetric analysis to understand the effect of a catalyst within the sulfur–iodine reaction system context. The findings of this analysis were also related to a thermodynamic assessment. It was observed that the presence of Pd/Al2O3 modified the reaction mechanism, possibly with some intermediate reactions that were suppressed or remarkably accelerated. The proposed model suggests that zinc sulfate transformation occurred in two sequential stages without the Pd-based material. Activation energy values of 238 and 368 kJ.mol−1 were calculated. In the presence of Pd/Al2O3, an activation energy value of 204 kJ.mol−1 was calculated, which is lower than observed previously.

Thermogravimetric/Thermal–Mass Spectroscopy Insight into Oxidation Propensity of Various Mechanochemically Made Kesterite Cu2ZnSnS4 Nanopowders

“…This suggests that the primarily evolved sulfur compound is SO 3 , likely, from the decomposition of some sulfate groups present on the surface of the kesterite particles. Under the experimental conditions (suitably high temperatures, gas flow), the equilibration of Reaction 5 (vide intra) favors the increased proportions of SO 2 and O 2 , as underlined in many metal sulfate decomposition studies [ 22 , 24 , 26 , 36 ]. In this regard, the evolution of the sulfur oxides taking place up to ca.…”

“…Interestingly, that high temperature range is more complex now than under the neutral gas conditions. This could be looked at as the consequence of an efficient oxidation of kesterite towards the individual metal sulfates that decompose shortly afterwards with metal oxide formation via the oxysulfate derivatives at the definite temperatures below 880–900 °C [ 22 , 23 , 24 , 25 , 26 ]. The evolution of SO 3 /SO 2 and its completion by 880–900 °C is the final decomposition event, and no further weight changes take place in any of the nanopowders up to the final temperature of 1000 °C.…”

“…The hydrated zinc sulfates ZnSO 4 •nH 2 O, n = 1 to 7, are commonly exemplified by the stable monohydrate ZnSO 4 •H 2 O [ 23 , 24 ]. The latter compound is found by TGA to dehydrate in one step by 250 °C, which is followed by the decomposition of ZnSO 4 , first, at 700–800 °C to oxysulfate ZnO•2ZnSO 4 and, then, at 800–950 °C to ZnO with the release of gaseous SO 3 , as outlined in Reaction 2 [ 24 ]. 3ZnSO 4 •H 2 O → 3ZnSO 4 + ↑3H 2 O → ZnO•2ZnSO 4 + ↑SO 3 → 3ZnO + ↑2SO 3 …”

Ethanol Conversion to Propylene over Zn/Hβ Catalysts: Influence of Zinc Precursors

“…Moreover, a series of high diffraction peaks at 18.5, 26.2, 26.9, 29.2, 34.9, 35.6, 38.5, and 41.0 o assigned to the ZnSO4 were observed for Zn/H-S, indicating the presence of a significant quantity of ZnSO4 on the surface of Zn/H-S [29]. Since the decomposition temperature of ZnSO4 is significantly higher than 550 °C, most of the ZnSO4 on the Zn/H-S is well retained after calcination at 450 °C for 4 h [30]. In contrast, the diffraction peaks at 31.7, 34.4, 36.2, and 47.5 o corresponding to the (100), (002), (101), and (102) lattice planes of ZnO were obviously detected on both Zn/H-Ac and Zn/H-N, suggesting the presence of large-sized and well-crystallized ZnO [31].…”

Direct Conversion of Ethanol to Propylene over Zn-Modified HBeta Zeolite: Influence of Zinc Precursors

“…Moreover, a series of diffraction peaks at 18.5, 26.2, 26.9, 29.2, 34.9, 35.6, 38.5 and 41.0 • assigned to the ZnSO 4 (JCPDS 33-1476) were observed for Zn/HBeta-S, indicating the presence of a significant quantity of ZnSO 4 on the surface of Zn/HBeta-S [28]. Since the initial decomposition temperature of ZnSO 4 to ZnO•ZnSO 4 was around 700 • C, most of the ZnSO 4 compound on Zn/HBeta-S was well retained after calcination at 450 • C for 4 h [29]. In contrast, strong diffraction peaks at 31.7, 34.4, 36.2 and 47.5 • corresponding to the (100), (002), ( 101) and (102) lattice planes of ZnO (JCPDS 36-1451) were obviously detected on both Zn/HBeta-Ac and Zn/HBeta-N, suggesting the presence of large-sized and well-crystallized ZnO [30].…”